I think if there was enough hype for WP7 then it would be worth building out Waze for it. As it is, 2 days after launch, it''s probably not worth it to them to dedicate resources to it. And it is a completely different os from WinMo 6.x. I wish I knew more about coding. I'd love to port it over for WP7. I'm just not that good at it.

I think the reason is simple: the developers have their hands full with the code and platforms they already have. Some users have complained that the developers are already spread too thin. So adding a new platform that the developers may have little or no experience with doesn't sound like an effective use of time when the other platforms still have major bugs/issues.